1. Field of the Invention
The present invention relates to a method for driving a liquid crystal panel, and a liquid crystal display device, and particularly to a method for driving an active matrix type liquid crystal panel that can surely display an image irrespective of peripheral temperature of the liquid crystal panel, and a liquid crystal display device.
2. Description of the Related Art
Recently, liquid crystal display devices have been applied for various kinds of applications under various environments. For example, with respect to peripheral temperature, it is required that these devices are excellently operated at from a high-temperature to a low-temperature.
Furthermore, TFT (Thin Film Transistor), TFD (Thin Film Diode), etc. are known as switching elements for the active matrix type liquid crystal display devices. Particularly, from the viewpoint of the image quality, TFT has been recently mainly used. In general, the charging performance of TFT has temperature dependence, and as the temperature is lowered, the charging performance is reduced. Therefore, in a line inverting driving method broadly used as a method of AC-driving each frame of the liquid crystal cell or a dot inversion driving method, charging to pixels is insufficient under such a environment that the peripheral temperature is relatively low, and no desired voltage is applied to liquid crystal (in the following description, the peripheral temperature means the temperature of the liquid crystal panel or temperature near the liquid crystal panel). As a result, in a normally white mode using general TN (Twist Nematic) type liquid crystal, the shift of the voltage-brightness characteristic to a high brightness side, increase of black brightness, reduction in contrast, etc. occur, and thus there is a problem that the image quality is degraded. Likewise, a normally black mode has problems such as the shift of the voltage-brightness characteristic to a low brightness side, disturbance of uniformity in brightness under high-brightness state, reduction of contrast due to reduction of white brightness, etc.
In order to prevent degradation of the image quality under the low-temperature condition, there is known a method for driving a liquid crystal panel in which every two scan lines are successively selected from plural scan lines under the low-temperature condition, and before a liquid crystal cell is charged at the original gradation potential corresponding to an image data signal, the liquid crystal cell concerned is preliminarily charged at the gradation potential corresponding to a liquid crystal cell which is preceding to the liquid crystal cell concerned by one or more lines and has the same color arrangement as the liquid crystal cell concerned (see JP-A-Hei. 10-186326).
Furthermore, in order to avoid an erroneous display caused by delay of display under the low-temperature condition, there has been proposed a method of connecting a display RAM to an LCD controller, making a display on the basis of image data of one frame written in RAM, and renewing image data written in RAM at the time interval corresponding to the peripheral temperature (see JP-A-Hei. 9-211427).